1. Field of the Invention
This invention relates to a method of judging presence of a frameless chemical analysis film in a cartridge, and more particularly to a method of judging whether there remains a frameless chemical analysis film in a cartridge in which a plurality of chemical analysis films are stored in a stack. The frameless chemical analysis film (including biochemical anlysis films and immunological anlysis films) is a film chip carrying thereon a reagent layer containing a reagent whose optical density changes through a chemical reaction, a biochemical reaction, an immunoreaction (immunological or immunochemical reaction) or the like with a specific biochemical component contained in a sample liquid such as blood or urine.
2. Description of the Prior Art
Quantitative or qualitative analysis of a specific component in a sample liquid is a common operation carried out various industrial, medical and clinical fields. Especially, quantitative analysis of a chemical or biochemical component or a solid component contained in body fluid such as blood or urine is very important in the field of clinical biochemistry.
There has been put into practice a xe2x80x9cdry-to-the-touchxe2x80x9d chemical or biochemical analysis film with which a specific component contained in a sample liquid can be quantitatively analyzed through a droplet of the sample liquid spotted on the slide. See Japanese Patent Publication No. 53(1978)-21677, (U.S. Pat. No. 3,992,158), Japanese Unexamined Patent Publication No. 55(1980)-164356, (U.S. Pat. No. 4,292,272) or the like. When such a dry chemical analysis film is used, the sample liquid can be analyzed more easily and more quickly than when the conventional wet analysis method is used, and accordingly the dry chemical analysis film is very convenient for medical facilities, laboratories and the like where lots of sample liquids have to be analyzed.
In a biochemical analysis apparatus for quantitatively analyzing chemical components or the like contained in a sample liquid using such a dry chemical analysis film, a droplet of the sample liquid is spotted on the film and is held at a constant temperature for a predetermined time (incubation) in an incubator so that coloring reaction adequately occurs, and the optical density of the color formed by the coloring reaction is optically measured. That is, measuring light containing a wavelength which is pre-selected according to the combination of the component to be analyzed and the reagent contained in the reagent layer of the film is projected onto the film and the optical density of the film is measured. Then the component to be analyzed is calculated on the basis of the optical density using a standard curve which represents the relation between the concentration of the biochemical component and the optical density. Thereafter the film is taken out from the incubator and discarded into a discarding box.
The chemical analysis film is generally composed of a support sheet of an organic polymer or the like and a reagent layer and a spreading layer formed on the support sheet and is conventionally generally provided with a plastic frame which holds the chemical analysis film flat which is apt to warp into a roof tile shape when it keeps in dried conditions. The chemical analysis film with frame is generally referred to as xe2x80x9cchemical analysis slidexe2x80x9d. However, the frame increases the volume and the size of the chemical analysis film and results in increase in the size of various parts handling the film such as cells in the incubator for incubating the chemical analysis films, the film transfer system, the film supplier for storing the films, the film cartridges and the like. Thus the frame of the chemical analysis film is obstructive to reducing the size of the biochemical analysis apparatus and at the same time reduces the film accommodating capacity of the incubator, which obstructs increase in handling capability of the overall biochemical analysis apparatus. Further the cost of mounting the frame is high, which adds to the cost of biochemical analysis.
In a biochemical analysis apparatus we have proposed previously, the film chip is used as it is without frame (will be referred to as xe2x80x9cframeless chemical analysis filmxe2x80x9d, hereinbelow). For example, in the biochemical analysis apparatus disclosed in Japanese Unexamined Patent Publication No. 5(1993)-188058 (corresponding to EP 0 555 654A2) or Japanese Unexamined Patent Publication No. 6(1994)-213903 (corresponding to EP 0 567 067A), a plurality of the frameless chemical analysis films are loaded in a cartridge and are taken out from the cartridge by means of an attracting means such as a reduced pressure suction cup in order to prevent damage to the film.
In such a biochemical analysis apparatus, a plurality of cartridges in which different types of frameless chemical analysis films (films for different analytes: biochemical components to be analyzed) are stored are set in the apparatus. When an analyte is designated, one of the cartridges in which frameless chemical analysis films corresponding to the analyte are stored is set to a film takeout position, the attracting means is moved to the film takeout position and then suction force (reduced pressure) is applied to the attracting means to attract one of the frameless chemical analysis films in the cartridge which is nearest to the film takeout position. Thereafter the attracting means is moved in a predetermined direction while holding the frameless chemical analysis film under the suction force to take out the film through a film takeout port in the cartridge. These operations are automatically carried out according to a predetermined program stored in the biochemical analysis apparatus.
When there remains no film in the cartridge set to the film takeout position, the series of the operations for taking out the film becomes vain, which deteriorates analyzing efficiency of the apparatus. Accordingly it is preferred that whether there remains some films in the cartridge be detected in advance and when no film remains in the cartridge, the operations for taking out the film from the cartridge be abandoned and the operations for taking out the film from another cartridge be effected immediately while alarming the operator absence of film (that there remains no film in the cartridge) by means of a buzzer, a lamp, a display or the like.
As disclosed in U.S. Pat. No. 4,190,420, there has been known a system in which whether there remains some chemical analysis slides in a cartridge is judged by means of a limit switch. That is, as shown in FIGS. 16A and 16B, a plurality of chemical analysis slides 250 (though only one slide is shown in FIG. 16A) are stacked in a cartridge 210 and a pressing member 232 is received in the cartridge 210 to be movable up and down in the cartridge 210. When a slide 250 is to be taken out, the pressing member 232 is pushed upward by a plunger 228 and presses the stack of the slides against the inner surface of a support portion 252 which projects downward from the top wall of the cartridge, thereby bringing the uppermost slide to a slide exit port (not shown) formed in a side wall of the cartridge 210. (FIG. 16A) In this state, the uppermost slide 250 is pushed transversely by a blade 222 through the slide exit port whose width is slightly larger than the thickness of the slide 250.
The width of the blade 222 is smaller than that of the slide 250 and the space between abutment edges 234 and 236 of the pressing member 232 is smaller than the width of the slide 250 and larger than the width of the blade 222 and the width of the support portion 252. Accordingly when the last slide 250 is pushed out of the cartridge 210, the abutment edges 234 and 236 of the pressing member 232 are moved upward beyond the lower surface of the support portion 252 into the spaces 254 and 256 between the support portion 252 and the side wall of the cartridge to abut against the bottoms of the spaces 254 and 256 as shown in FIG. 16B. In response to the upward movement of the pressing member 232, the plunger 228 moves upward and a pin 248 projecting from the side of the plunger 228 pushes upward a contact 246 of a limit switch 244 to turn on the limit switch 244. When the limit switch 244 is turned on, an alarm means such as a buzzer, a lamp or a display is energized to alarm the operator that no slide remains in the cartridge 210.
In the prior art described above, the stack of the slides 250 is pushed upward by the plunger 228 by way of the pressing member 232 in order to surely set the uppermost slide to a position suitable for taking out the slide. Further the slide 250 must be kept pressed by the pressing member 232 so that the abutment edges 234 and 236 are inserted into the spaces 254 and 256 in response to pushing out the last slide. That is, the stack of the slides 250 is pressed under a relatively large pressure in order to surely bring the uppermost slide to the takeout position and to surely detect presence or absence of the slide.
As a result, substantially the same portions of the stack of the slides are subjected to a large pressure by the abutment edges 234 and 236 every time the uppermost slide is taken out.
In the case of the chemical analysis slide 250, the chemical analysis film itself is not so damaged so long as the abutment edges 234 and 236 are brought into abutment against the frame of the slide 250.
However when the system of the prior art is applied to the frameless chemical analysis films as it is, the abutment edges 234 and 236 are brought into a direct contact with the surface of the lowermost film and the surface of the lowermost film is kept subjected to a large pressure for a long time. Further the films on the lowermost film are indirectly subjected to the pressure. Further since the uppermost film is transversely slid with the stack of the films kept pressed, friction adversely affects the uppermost film when it is taken out.
That is, the film can be bent or folded or peeled under the influence of the friction generated by the pressure. Further when the spreading layer of the film is kept subjected to a large pressure, condition of the spreading layer changes and the sample liquid spreading speed changes, whereby the measuring accuracy can deteriorate.
In order to overcome such problems, the means for taking out the films and the means for judging presence or absence of the films must be properly arranged and laid out not to interfere with each other.
In view of the foregoing observations and description, the primary object of the present invention is to provide a method of judging presence of a frameless chemical analysis film in a cartridge in which whether there remains a frameless chemical analysis film can be judged without fear of damaging the film and the means for carrying out the method can be disposed without being restricted by the means for taking out the film.
In accordance with the present invention, there is provided a method of judging presence of a frameless chemical analysis film in a cartridge in which a plurality of the frameless chemical analysis films are stacked, characterized in that whether or not there remains a frameless chemical analysis film in the cartridge is detected by a film presence detecting means disposed in a second position different from a first position where a film takeout means takes out the frameless chemical analysis films from the cartridge so that the film presence detecting means does not interfere with the film takeout means.
It is preferred that the film presence detecting means detects whether or not there remains a frameless chemical analysis film in the cartridge in the second position with the frameless chemical analysis films pressed toward a film takeout port under a force which is not larger than a force required to make the frameless chemical analysis films completely flat.
In accordance with the method of the present invention, whether or not there remains a frameless chemical analysis film in the cartridge is detected in a position different from a position where the frameless chemical analysis films are taken out from the cartridge.
That is, the frameless chemical analysis films are taken out from the cartridge in the first position by a film takeout system using, for instance, a vacuum (reduced pressure) attracting means.
Since the vacuum attracting means is moved outside the film takeout port in the vicinity thereof, it is difficult to dispose the film presence detecting means near the film takeout port.
Accordingly, in accordance with the method of the present invention, the second position where whether or not there remains a frameless chemical analysis film in the cartridge is detected is spaced from the first position where the film takeout means takes out the frameless chemical analysis films from the cartridge, and the film presence detecting means is disposed in the second position.
When the frameless chemical analysis films are pressed toward the film takeout port, the films which are apt to be variously curled or warped in the dry state are reshaped into a substantially uniform shape, whereby accuracy in detecting whether there remains a film in the cartridge can be improved without being affected by curl or warp of the films.
When the force under which the films are pressed is not larger than a force required to completely remove the curl or warp of the frameless chemical analysis films and render them completely flat, the films can be taken out without damage on the surfaces thereof unlike in the aforesaid prior art where the slides are pressed under a large force when they are taken out.